Researchers at The University of Western Australia and Monash University have discovered dietary antioxidants can help maintain male fertility.

Dr Maria Almbro and Winthrop Professor Leigh Simmons, from UWA's Centre for Evolutionary Biology, and Dr Damian Dowling, from Monash University's School of Biological Sciences, studied crickets and found that a combination of antioxidants provided the best weapon to boost the health of the male ejaculate. The study was published today in the prestigious journal Ecology Letters.

Professor Simmons said highly reactive molecules, known as free radicals were waste products of the cellular processes that fuel the body's activities. "These free radicals damage cells if they are not neutralised by antioxidants," he said.

Dr Almbro said sperm were known to be vulnerable to attack from free radicals, and the study had shown that the best defence against sperm damage was to take two antioxidants; Vitamin E and beta-carotene.

Professor Simmons said for most animals, it was typical for females to have the sperm of several males inside them at any given time, competing for the fertilisation of the eggs.

"It is fair to say that the sperm are at war within the female, and we can expect that the most competitive sperm will win the race to the egg. Our study showed that the sperm of males who were fed antioxidants were easily able to outclass the sperm of rival males who were deprived of antioxidants."

Dr Dowling said medical scientists had already provided evidence that antioxidants were important in maintaining sperm health.

"What we have done is provide a definitive experimental confirmation of this, not in a test tube, but in a real living animal, showing that antioxidants are profoundly important in deciding the outcomes of reproduction in males.

"That is to say, antioxidants in the diet equal more babies, at least in these crickets. And by working with crickets rather than humans as subjects, we were able to conduct the experiment under very strictly controlled conditions - ruling out all other alternative explanations for our results."

The researchers will now determine the precise mechanism by which dietary antioxidants enhance male fertility in these insects.